Field of Endeavor
The present invention relates to methods of applying multiple different materials with selective laser melting on a 3D article as well as to 3D articles, in particular turbine components and parts thereof.
Brief Description of the Related Art
Methods for manufacturing a molded body, e.g., a prototype of a product or component, a tool prototype or spare part, in accordance with three-dimensional CAD data of a model of a molded body, by depositing layers of a liquid material or a metallic material in powder form, have become increasingly popular and commercially important.
One of these methods is known as stereo lithography. In stereo lithography, a molded body to be manufactured is divided into individual layers and the data of the individual layers concerning the prototype to be manufactured are supplied to a manufacturing device. Such a manufacturing device consists of a liquid bath with a UV hardening liquid that a UV beam sweeps over according to the contours and fields of the prototype to be manufactured in order to harden the liquid. Then, this initial layer is lowered to a defined layer thickness in order to harden a second coating on to it in accordance with the established data. Layer by layer this process continues until the entire model or prototype is created. Thin pipe walls, hollow cavities or intertwined components can be manufactured in a manner that corresponds to the serial product. Depending on the degree of partitioning of the layers, that is, the thickness of each layer that is hardened, even curvatures can be built in detail, within the general process limits.
Further methods of building a prototype of sintered metallic material in powder form are known, also designated as direct metal laser sintering (DMLS), selective laser melting (SLM), or electron beam melting (EBM). Such a method is, e.g., described in WO 92/10343. According to the method described in WO 92/10343, in order to manufacture a component, a first layer of powder that can be sintered is deposited and the powder is sintered according to the layer areas of the part to be manufactured. Then, this method is repeated in a manner where each time a new layer is deposited on the previously sintered layer and where these layers correspond to the respective layers or cross-sectional areas of the component to be manufactured. Also, WO 98/24574 discloses a method in which several layers of the powder are successively deposited one on top of the other, whereby each layer of powder is heated to a specified temperature by a focused laser beam applied to a given area corresponding to a selected cross-sectional area of the model of the molded body, before deposition of the next layer. The laser beam is guided over each layer of powder in accordance with the CAD cross-sectional data of the selected cross-sectional area of the model in such a way that each layer of powder is fixed to the layer below.
DE 102 19 983 discloses a method for making metallic or non-metallic products by freeform laser sintering, in which the products are fabricated from powdery material on a substrate plate in vertically additive, layer-by-layer fashion by a computer-controlled laser beam. Here, in particular for solving problems with the use of such a method for the production of small parts, the method is characterized in that at least one support is fabricated between the substrate plate and the outer surface of the product, the support being connected via a predetermined breaking area with the outer surface of the product, wherein the predetermined breaking area is formed by reducing the strength of the support along the outer contour of the product.
WO 2008/155021 also relates to a method for producing a component based on three-dimensional data for the component which is characterized in that, to produce the component from at least two different materials in defined regions of each of the cross-sectional regions, a type of powder is applied corresponding to the material of the cross-sectional region and the applied powder of the powder layer is fused by energy radiation suitable for the powder type.
One of the problems associated with these methods is the delivery of the powder for the individual steps. Therefore, particular devices have been proposed to this end. U.S. Pat. No. 6,672,343, for example, discloses an apparatus for delivering powder onto a plane surface of a device for creating a three-dimensional part in a layer-by-layer fashion, in particular of a laser sintering machine. It includes a covering device which can be moved back and forth in a second direction perpendicular to a first direction by a drive between a lateral first position and a second position located on the opposite side. In at least one of the positions it can be filled with powder. In order to simplify the apparatus and improve its operation, the covering device includes a slit extending across the entire width and open at its top and its bottom as well as smoothening elements at the ends opposite of the surface. A store container is provided above the coveringdevice, the volume of the store container at each location across the entire width being at least equal to the volume of the slit cavity located underneath.
In order to treat the surface of direct metal laser sintered materials to improve corrosion resistance and reduce surface defects, U.S. Patent Application Publication No. 2007/141375 proposes a direct metal laser sintered material including a substrate formed from a laser sintering process, the substrate having at least one surface, and a cladding material brazed onto at least a portion of the surface.
Apart from prototype manufacturing, DMLS is also used for the production of engine parts. For example, U.S. Patent Application Publication No. 2001/014403 discloses a method and an apparatus for fabricating a component by a direct laser process. One form embodying principles of the present invention contemplates a gas turbine engine blade having an abrasive tip formed directly thereon. U.S. Pat. No. 6,861,613 also discloses a generative method of fabrication and an accompanying device with which components can be fabricated in a DMLS process, but this time from a combination of materials using different types of metal powders. The device includes a bottom surface with a lowerable building platform, a leveling mechanism for leveling a first material in a processing plane above the building platform, a laser beam source for emitting a laser beam, a processing unit with a focusing optical system for focusing the laser beam onto the processing plane and a positioning mechanism which can position the processing unit in any desired positions in a plane parallel to the processing plane above the component. Furthermore, the device is provided with a suction device for sectioning off the material from the processing plane and an introduction mechanism for a second material with which the latter is brought into the focal range of the laser beam. This device permits fabrication of components of any desired complexity and adapted to a certain function, in which individual regions can be made of a second, harder material to increase sturdiness or to improve wear-resistance.
3D articles manufactured with SLM process are conventionally built up on a platform in a movable powder bed. The state of the art process is to build up the 3D article by melting metal powder (first material) in a multiple layer arrangement using a laser beam. In order to apply a second material (different metal powder), the first material has to be removed completely with great efforts or the powder bed is contaminated. Possible methods and devices to locally remove previously deposited first material powder with a suction or blow-off device are expensive, slow and may not avoid powder contamination. Therefore the layer-wise powder SLM process can not efficiently be used for this task and a laser generating process such as DMD (Direct Metal Deposition)/LENS (Laser Engineered Net Shape) has to be integrated.